1. Field of the Invention
The present invention relates to a wire connection structure having a surge suppressing effect and a noise reduction unit and a wire harness having the wire connection structure.
2. Description of the Related Art
In general, in electric vehicles, hybrid vehicles, etc., DC power of a battery or the like is converted into AC power by an inverter and a motor for rotating wheels and a motor generator (hereafter referred to generically as a “motor”) are driven using the AC power. In inverters of this kind, since they convert DC power into AC power by switching the former at a high frequency, there may occur an event that high-frequency surge currents generated by the switching flow through the load motor. Various surge control methods for inverters have been proposed to prevent dielectric breakdown or the like of the motor by such surge currents.
For example, as shown in FIG. 11, JP-A-2012-174661 discloses a connector device 501 which is equipped with noise reduction coils. Among two power supply AC wires 505a and 507a and one ground wire 513 which are inserted through a cylindrical portion 503 of the connector device 501 and go out of one end surface of the cylindrical portion 503, the two power supply AC wires 505a and 507a are wound around two respective toroidal cores 509a which is disposed around (i.e., fitted with) the cylindrical portion 503. The cylindrical portion 503 is formed with grooves 511a in which the portions, wound around the toroidal cores 509a, of the power supply AC wires 505a and 507a are placed, respectively. Two through-holes 511b penetrate through the circumferential wall of the cylindrical portion 503, and AC wires 505b and 507b for power line communication which are connected to respective AC wires 505 and 507 inside the cylindrical portion 503 are inserted through the through-holes 511b to go out of the cylindrical portion 503.
In the connector device 501, noise reduction is attained by coils that are formed in such a manner that the power supply AC wires 505a and 507a which extend from the cylindrical portion 503 are wound around the respective toroidal cores 509a. 
However, since the coils are formed by winding the wires (power supply AC wires 505a and 507a) around the ring-shaped magnetic bodies, the above conventional connector device 501 has a problem that its overall size is large because of a restriction relating to a minimum wire bending radius. In particular, as the wire diameter increases as in the case of high-voltage cables, the minimum wire bending radius becomes larger to make it difficult to install the connector device 501 in a vehicle. There is another problem that a winding process requires a number of steps.